Variability in flavonol content of grapes cultivated in two Mediterranean islands (Sardinia and Corsica)

The main abundant flavonols, myricetin, quercetin and kaempferol, were analyzed in 58 samples of native red and white grapes from two Mediterranean islands, Sardinia and Corsica, with the aim of identifying a possible correlation between the respective flavonol profile and varietal origin. Quercetin and myricetin are the most commonly represented flavonols in the red grapes. In the white varieties quercetin prevails over kaempferol, while myricetin is absent. Absolute data show that the red varieties of Nielluccio and Minustello present high total concentrations of flavonols. Among the white grape varieties it is possible to observe that the Moscato is characterized by a total flavonol content clearly higher than that of Vermentino, and comparable to, sometimes even higher than, that of the other red varieties. No differences have been found between the Vermentino samples from Corsica and Sardinia according to their geographical origin. Considering the absolute values of the compounds analyzed great variability is found among the samples belonging to the same variety, whereas variability in the flavonol profile, expressed as percentage content of each aglycon of the total, is less pronounced. Statistical techniques (ANOVA and Hierarchical Cluster Analysis) showed that the flavonol profile, rather than the absolute values, enabled good discrimination between cultivars, demonstrating that it may effectively be used for chemotaxonomic aims.